This invention relates generally to a steering mechanism for an agricultural tractor in which the front axle is laterally shiftable in response to a steering movement of the steerable wheels and, more particularly, to a ballast assembly for such laterally shiftable front axle steering mechanisms to maintain proper weight distribution on the steerable wheels as the front axle shifts laterally.
Tractors, whether used in an agricultural setting or in an industrial setting, typically include a fixed axle through which primary driving power is transferred through fixed wheels rotatably mounted on opposing ends of the fixed axle, and a steering axle having pivotally mounted steerable ground engaging wheels rotatably mounted on the opposing ends thereof to support the chassis of the tractor above the ground. Although supplemental driving power is often provided to the steerable ground engaging wheels, a steering mechanism remotely controllable by the operator from the operator's compartment selectively controls the pivotal movement of the steerable wheels relative to the steering axle.
One such steering mechanism incorporates a transversely disposed, horizontally extending hydraulic cylinder supported by the steering axle and connected to the opposing steerable wheels. This hydraulic cylinder affects pivotal movement of the steerable wheels about their respective pivotal connections to the steering axle by manipulating the pressures in the hydraulic cylinder to effect a transverse extension of the cylinder rod, causing a turning of the wheels.
Due to physical limitations relating to the range of movement of the steering mechanism and to the eventual interference between the steerable wheels and the steering axle or chassis frame, the amount of pivotal movement of the steerable wheels relative to the steering axle is limited to a given turning angle. This maximum turning angle defines the minimum turning radius of the tractor for a given wheel base length and tread spacing. The selection of the length of the wheel base, i.e., the distance between the fixed axle and the steering axle, is a compromise between the need to minimize the turning radius and, therefore, minimize the wheel base length, and to maximize ride considerations which require longer wheel base lengths.
These conflicting wheel base requirements can be better resolved by a steering mechanism incorporating a laterally shifting front axle that is movable in response to a corresponding steering movement of the steerable wheels, which will decrease the turning radius of the tractor for any given wheel base length.
Traditionally, the front of the tractor is provided with added ballast or weights to improve weight distribution for the tractor during its operation and, thereby, increase traction for the front steerable wheels. Such weights are normally mounted in a detachable manner to the forward part of the tractor chassis; however, for tractors in which the front axle would shift laterally relative to the chassis, such chassis mounted weights would become unevenly distributed to the steerable wheels since one steerable wheel moves closer to the weights than the other steerable wheel.
It would, therefore, be desirable to provide a ballast assembly usable with a tractor having a laterally shiftable front axle that would maintain a positional relationship between the ballast and the front wheels to which the weight is distributed. Such ballast could be formed from individual weights to create an arcuate ballast assembly with the center of gravity thereof being spaced further away from the front axle than previously known.